In an induction motor if air-gap is increased

A wound rotor induction motor is preferred, as compared to squirrel cage induction motor, when major consideration is

A

Slop speed operation

B

High starting torque

C

Low windage losses

D

All of the above

While starting a synchronous motor by induction motor action, field winding is usually

A

connected to D.C. supply

B

short-circuited by low resistance

C

kept open-circuited

D

none of the above

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because

A

synchronous motor has no slip

B

stator supply is not required to produce magnetic field

C

mechanical load on the rotor remains constant

D

synchronous motor has large airgap

While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by

A

induction motor torque in field winding

B

induction motor torque in damper winding

C

eddy current and hysteresis torque in pole faces

D

reHetance motor torque due to saliency of the rotor

E

all of the above methods

Slip ring motor is preferred over squirrel cage induction motor where

A

High starting torque is required

B

Load torque is heavy

C

Heavy pull out torque is required

D

All of the above

The power factor of a synchronous motor is better than that of induction motor because

A

stator supply is relieved of responsibility of producing magnetic field

B

mechanical load on the motor can be adjusted

C

synchronous motor runs at synchronous speed

D

synchronous motor has large air gap

An important advantage of a synchronous motor over wound round induction motor is that

A

its power factor may be varied at will

B

its speed is independent of supply frequency

C

its speed may be controlled more easily

D

none of the above

The starting torque of a three phase induction motor can be increased by

A

Increasing slip

B

Increasing current

C

Both (A) and (B)

D

None of the above

The stating torque of the slip ring induction motor can be increased by adding

A

External inductance to the rotor

B

External resistance to the rotor

C

External capacitance to the rotor

D

Both resistance and inductance to rotor

In case the air gap in an induction motor is increased

A

The magnetizing current of the rotor will decrease

B

The power factor will decrease

C

Speed of motor will increase

D

The windage losses will increase

In an induction motor if air-gap is increased

Related Questions